[daip] CALIB feature

[Eric Greisen]

Jim Ulvestad writes:
 > If you have a VLBA data set that you're trying
 > to self-calibrate, and the data set is all one
 > polarization, you get in big trouble by
 > specifying aparm(3)=1 (average RR and LL) in
 > CALIB.  In this case, CALIB apparently does
 > the models, gets to the point where it says
 > it's writing the SN table, and then goes into
 > an infinite loop and stays there forever.
 > 
 > Obviously, this is user error for not remembering
 > how a data set was observed several years ago,
 > but it would be nice if it croaked a little more
 > obviously.
 > 

I put in blocks with a message about IF and pol averaging right at the
start.  Please test this tomorrow.

E